1. Field of the Invention
The present invention pertains to multilayered structural elements which are useful for forming housings for electronic devices such as cellular telephones.
2. Description Of The Related Art
It is well known in the art that housings for electronic devices, such as cellular telephones, which are made of plastics, are becoming progressively thinner as the overall size of these devices decrease. Electronic device manufacturers seek housing space reductions to contribute to an overall reduction in the size of electronic devices as demand increases for smaller sizes of such devices.
Current cellular telephone housings are manufactured by a series of manufacturing steps requiring injection molding, individual manufacturing operations and final assembly. This technique has several drawbacks.
The housings lose stiffness as the walls become thinner. These can be reinforced, such as with fiber glass only to a limited extent because of glass breakage, an increase in viscosity, and appearance issues. Injection molds can be filled very quickly at higher pressures and/or melt temperatures to prevent premature solidification, but these conditions can cause appearance and degradation problems. In addition, modified injection molding machines are very costly.
Certain surfaces of the housing must be coated with an EMI shielding material in a secondary operation. Decorated surfaces require placing a preformed plastic film in the injection mold and filling the mold behind the film without distortion or degradation of the film. Soft touch surfaces on the device may require two-step molding and the associated tool expense. Current electronic devices are not shaped to conform to the user""s hand. The keypads, which are relatively thick, are molded separately and assembled by aligning with holes in the cover of the housing. Assembly of the covers and internal components requires the use of screws or other fasteners. The current design with air gaps between the internal components and the housing is not suited for removing heat generated internally. An external antenna is assembled as a separate step and requires threaded inserts causing local stress concentrations and cracks. Current antennas have no directionality, and exposure of the user""s head to high frequency radiation is of increasing concern.
It would be beneficial to produce a housing for electronic devices that has a thin, tough, stiff, decorated, shielded, and compact, shaped housing. For example, such a housing could be used to produce cellular telephones as thin as two thick credit cards, that can be carried in a shirt pocket. To this end, the invention provides thin, a multilayered structural element for electronic circuitry having a thin, flexible polymeric outer film layer, an optional electronic interface layer having a pattern of electrically conductive lines; a rigid structural layer; an electromagnetic interference shielding layer; and an optional protective layer.
The related art describes a variety of housings for electronic devices, however, the multilayered structural element of this invention is not suggested. U.S. Pat. Nos. 4,227,037; 5,520,976; 5,700,342; 5,804,762; 5,595,801 and 5,819,16 EMI shielded enclosure for electronic devices. U.S. Pat. No. 5,837,086 shows a method of injection molding plastics for electrical shielding. U.S. Pat. No. 6,005,191 shows a heat shrinkable sheathing for coaxial cables. U.S. Pat. No. 4,678,699 shows an EMI/RFI shielding composite, however, such does not have an electronic interface layer having a pattern of electrically conductive lines. U.S. Pat. No. 3,931,094 shows a filled thermoplastic composition for forming shaped articles.
The present invention solves a multitude of problems associated with injection molding operations and related secondary operations, assembly and manufacturing processes by providing a new structure and processing for thin electronic and other housings. The structure comprises a multifunctional laminate in which each thin layer of laminated material performs one or more of the following functions: stiff impact resistant covering, decorated/soft touch external surfaces, transparent screen cover, integral key pad, EMI shielding, thermal management, and internal antenna. The design of the electronic device integrates internal electronic components and a reinforced housing which simultaneously provides and a heat conduction path for the electronic components. A process for manufacturing the housing according to the present invention comprises a continuous lamination line in which various layers are brought together, bonded, and shaped to produce an assembled housing section substantially in its final form. Alternatively the housing can be manufactured by stacking the various layers as discrete pieces, obtaining the proper registration among layers, and shaping the assembled layers between the surfaces of a heated tool. The present invention overcomes the limitations and problems associated with the injection molding process because the new design uses a continuous fiber reinforced laminate which is very tough, stiff, and thin. Additionally, the external surface of the housing may be covered by a decorative layer of an aesthetic material, and an integral conductive film layer provides EMI shielding.
The invention provides a multilayered structural element for attachment to electronic circuitry which comprises as sequentially attached layers:
(a) thin, flexible polymeric outer film layer,
(b) an electronic interface layer, the electronic interface layer comprising a thin, flexible polymeric film layer having a pattern of electrically conductive lines on at least one side thereof;
(c) a rigid structural layer;
(d) an electromagnetic interference shielding layer; and
(e) an optional protective layer.
The invention also provides an electronic device which comprises an electronic circuit element and the above structural element attached on a side of the circuit element, such that the circuit element is attached to the electromagnetic interference shielding layer or the protective layer; and the conductive lines of the electronic interface layer form an electric connection with the circuit element.
The invention further provides an electronic device which comprises as sequentially attached elements:
i) a first multilayered structural element which comprises as sequentially attached layers:
(a) a thin, flexible polymeric outer film layer,
(b) an electronic interface layer, the electronic interface layer comprising a thin, flexible polymeric film layer having a pattern of electrically conductive lines on at least one side thereof;
(c) a rigid structural layer;
(d) an electromagnetic interference shielding layer; and
(e) an optional protective layer;
ii) an electronic circuit element attached to the electromagnetic interference shielding layer or the protective layer of the first multilayered structural element wherein the conductive lines of the electronic interface layer forms an electric connection with the circuit element; and
iii) a second multilayered structural element, which comprises as sequentially attached layers:
(a) a thin, flexible polymeric outer film layer,
(b) an optional electronic interface layer, the electronic interface layer comprising a thin, flexible polymeric layer having a pattern of electrically conductive lines on at least one side thereof;
(c) a rigid structural layer;
(d) an electromagnetic interference shielding layer; and
(e) an optional protective layer;
the circuit element being attached to the electromagnetic interference shielding layer or the protective layer of the second multilayered structural element.
The invention still further provides a telephone which comprises a first telephone half hingedly and electrically connected to a second telephone half, each telephone half comprising as sequentially attached elements:
i) a first multilayered structural element, which comprises as sequentially attached layers:
(a) a thin, flexible polymeric outer film layer,
(b) an electronic interface layer, the electronic interface layer comprising a thin, flexible polymeric film layer having a pattern of electrically conductive lines on at least one side thereof;
(c) a rigid structural layer;
(d) an electromagnetic interference shielding layer; and
(e) an optional protective layer attached;
ii) an electronic telephone circuit element attached to the electromagnetic interference shielding layer or the protective layer of the first multilayered structural element, wherein the conductive lines of the electronic interface layer forms an electric connection with the telephone circuit element; and
iii) a second multilayered structural element, which comprises as sequentially attached layers:
(a) a thin, flexible polymeric outer film layer,
(b) an optional electronic interface layer, the electronic interface layer comprising a thin, flexible polymeric film layer having a pattern of electrically conductive lines on at least one side thereof;
(c) a rigid structural layer;
(d) an electromagnetic interference shielding layer; and
(e) an optional protective layer;
the telephone circuit element being attached to the electromagnetic interference shielding layer or the protective layer of the second multilayered structural element.
The invention still further provides a process for producing a multilayered structural element for attachment to electronic circuitry which comprises continuously or discretely attaching as sequential layers:
(a) a thin, flexible polymeric outer film layer,
(b) an optional electronic interface layer, the electronic interface layer comprising a thin, flexible polymeric film layer having a pattern of electrically conductive lines on at least one side thereof;
(c) a rigid structural layer;
(d) an electromagnetic interference shielding layer; and
(e) an optional protective layer.
The invention still further provides a process for producing an electronic device which comprises producing first and second multilayered structural elements by continuously attaching as sequential layers:
(a) a thin, flexible polymeric outer film layer,
(b) an optional electronic interface layer, the electronic interface layer comprising a thin, flexible polymeric film layer having a pattern of electrically conductive lines on at least one side thereof;
(c) a rigid structural layer;
(d) an electromagnetic interference shielding layer; and
(e) an optional protective layer; and
attaching the first and second multilayered structural element on opposite sides of an electronic circuit element, such that the circuit element is attached to the electromagnetic interference shielding layer or the protective layer of each structural element; wherein at least one electronic interface layer is present and the conductive lines of the electronic interface layer form an electric connection with the circuit element.
The invention still further provides a process for producing an electronic device which comprises producing first and second multilayered structural elements by continuously or discretely attaching as sequential layers:
(a) a thin, flexible polymeric outer film layer,
(b) an optional electronic interface layer, the electronic interface layer comprising a thin, flexible polymeric film layer having a pattern of electrically conductive lines on at least one side thereof,
(c) a rigid structural layer;
(d) an electromagnetic interference shielding layer; and
(e) an optional protective layer; and
attaching the first and second multilayered structural element on opposite sides of a circuit element, such that the circuit element is attached to the electromagnetic interference shielding layer or the protective layer of each structural element; wherein at least one electronic interface layer is present and the conductive lines of the electronic interface layer form an electric connection with the circuit element.
The invention still further provides a process for producing a telephone which comprises
i) forming first and second telephone halves, each telephone half being produced by producing first and second multilayered structural elements by continuously or discretely attaching as sequential layers:
(a) a thin, flexible polymeric outer film layer,
(b) an optional electronic interface layer, the electronic interface layer comprising a thin, flexible polymeric film layer having a pattern of electrically conductive lines on at least one side thereof;
(c) a rigid structural layer;
(d) an electromagnetic interference shielding layer; and
(e) an optional protective layer; and
ii) attaching the first and second multilayered structural element on opposite sides of a telephone circuit element, such that the telephone circuit element is attached to the electromagnetic interference shielding layer or the protective layer of each structural element; wherein at least one electronic interface layer is present and the conductive lines of the electronic interface layer form an electric connection with the telephone circuit element;
iii) hingedly and electrically connecting the first and second telephone halves.